For example, when a disaster such as an earthquake or a tsunami occurs, a tank main valve used in a factory or plant needs to be quickly closed in order to maintain safety and prevent the drain of hazardous substances stored in a tank. If the safety of plant facilities is confirmed, so that an operation is resumed, the tank main valve is opened.
If a manual valve is provided as the tank main valve, a worker should go to the installation site of the valve and to open and close the valve by manual operations. Therefore, manual operations on the tank main valve may be impractical, depending on the scale and the configuration of the plant.
Thus, it has been put into practical use to realize remote control monitoring by, e.g., adding to an existing manual valve 10 an automatic switch 20 using an air motor that uses an air pressure as a power source, as illustrated in FIG. 11.
In FIG. 11, the automatic switch 20 consists of an air motor 21 using an air pressure as a power source, and an air circuit switching valve 22 for switching the rotational direction of the air motor 21 by switching a supply circuit for an air pressure that drives the air motor 21. The output shaft 21a of the air motor 21 is mechanically connected to a manual operating portion 11 of the manual valve 10.
An air source 30, and an operating panel 41 configuring an operating system 40 of the automatic switch 20 are connected to the automatic switch 20. The air source 30 supplies a drive air pressure and a control air pressure to the automatic switch 20 and the operating panel 41, respectively.
In addition, the automatic switch 20 is provided with an opening-side limit switch adapted to be switched when the manual valve 10 reaches an opening-side limit position, a closing-side limit switch adapted to be switched when the manual valve 10 reaches a closing-side limit position, an opening-side switching valve adapted to switch the circuit for the air motor according to an air pressure from the opening-side limit switch, a closing-side switching valve adapted to switch the circuit for the air motor according to an air pressure from the closing-side limit switch, and so on (though these switches and valves are not shown).
The operating system 40 is configured by the operating panel 41, an instrument-panel room 42, a control signal line 43 connecting the operating panel 41 and the instrument-panel room 42 to each other, and so on.
The operating panel 41 is provided with a solenoid valve that performs opening and closing operations for an air pressure supplied to the air motor 21 by switching the air circuit switching valve 22 according to a solenoid valve opening signal or a solenoid valve closing signal input from the instrument-panel room 42, an operation switching valve that switches between an operation of the manual valve 10 at the installation site of the manual valve 10 by a lever operation and an operation of the manual valve 10 remotely controlled from the instrument panel room 42, an opening/closing operation valve that performs opening and closing operations for an air pressure supplied to the air motor by switching the air circuit through a lever operation, an opening-side shuttle valve that outputs a control air pressure to the opening-side switching valve of the automatic switch 20, a closing-side shuttle valve that outputs a control air pressure to the closing-side switching valve of the automatic switch 20, an opening-status indication air lamp that indicates the operating-status of the opening-side limit switch, a closing-status indication air lamp that indicates the operating status of the closing-side limit switch, and so on (though these valves and lamp are not shown).
When an operation of the operation switching valve provided on the operating panel 41 is switched to an operation remotely controlled from the instrument-panel room 42 in such a configuration, so that a solenoid valve opening signal input to the operating panel 41 from the instrument-panel room 42 is turned on, and that the solenoid valve provided on the operating panel 41 operates to an opening-side, a drive control air pressure input to the operating panel 41 from the air source 30 reaches the opening-side of the air circuit switching valve 22 via the opening-side shuttle valve and the opening-side switching valve. Consequently, the air circuit switching valve 22 is switched to the opening-side, so that the drive control air pressure input to the automatic switch 20 from the air source 30 is supplied to the opening-side of the air motor 21, and that thus, the air motor 21 is rotated to the opening-side.
When the air motor 21 reaches the opening-side limit position, so that the opening-side limit switch is switched, a limit control air pressure is transmitted to the opening-side switching valve. Thus, the opening-side switching valve is switched to a closing-side. Consequently, the drive control air pressure does not reach the air motor 21. Then, when the solenoid valve opening signal input to the operating panel 41 from the instrument-panel room 42 is turned off at an appropriate timing, the solenoid valve returns to a central position from the opening-side.
If the air motor 21 is operated to the closing-side, a solenoid valve closing signal input from the instrument-panel room 42 to the operating panel 41 is turned on. Consequently, a closing-side circuit operates, so that the air motor 21 starts to rotate to the closing-side, so that the closing-side limit switch is switched, and that an operation is stopped.
Patent Document 1 discloses technology of controlling the opening and the closing of a valve, using a wireless signal.
Patent Document 2 discloses technology of remotely controlling a valve actuator laid in a secluded place among mountains or the like, using a communications satellite.